This invention relates to an arrangement and a method for liquid level measurement. The invention has particular, although not sole application, to the measurement of levels of electrically conductive liquids such as milk. The invention does however have application to the measurement of all electrically conductive liquids.
Up until this time, a number of mechanically passive arrangements and methods have been used and suggested for measuring liquid levels, such as including capacitance probes, relative conductivity, incremental probe using multiple electrode arrangements, ultra-sonic reflection and resonant cavity methods and the like.
In the measurement of the levels of liquids such as for example milk, it is required to have an accurate and relatively low powered system for measuring the level of milk, preferably within a container. For example a measuring container or chamber associated with a milk meter, such as that described in U.S. Pat. No. 3,349,617.
The measurement of such milk is required in association with sampling as is required in milking operations, in milking sheds in dairy factories and the like.
Up untii this time, none of the arrangements or methods used or known up until this time have been satisfactory, adequate or successful in allowing for the effective measurement of liquids such as milk.
For example, the capacitance probe arrangements have suffered from problems with hygiene and cleaning, in that cumulative contamination or build up on the dielectric material of the probes, has caused increasing measurement errors, with sustained or increasing use. The relative conductivity system suggested, while suitable for measurement of limited accuracy, has been shown to be seriously effected by variations in conductivity of liquid, (such as is commonly experienced with liquids such as milk).
An incremented probe arrangement using multiple electrodes, has been satisfactory with some liquids, but suffers from increase of measurement errors with time with organic liquids such as milk, because of the difficulty in keeping the electrodes clean.
The ultrasonic reflection and resonant cavity methods have been shown to be unsuitable because of their relatively high power requirements and usually relatively large size. This is a particular disadvantage where measuring arrangements and methods are to be used in milking sheds, dairy factories and the like, where it is desired to minimise expense, power use and the size of equipment and components.
The present invention sets out to provide an arrangement and method for the measurement of liquid levels, and to go someway to at least reducing these problems. The present invention also sets out to provide an efficient and straight forward measuring arrangement and method for use with liquids.